1. Technical Field
The disclosure contained in this document relates to a linkage for rotating mechanisms, and particularly to a linkage for coupling the rotating shafts of a high voltage circuit breaker or recloser in end-to-end relationship.
2. Description of the Related Art
High voltage circuit breakers are used in the distribution of three phase electrical energy to prevent the flow of current in a circuit when a fault or other disturbance is detected. When a sensor or protective relay detects a fault or disturbance in the circuit, current-carrying contacts in each of the three phases are physically separated to prevent current flow until the circuit is clear. A recloser is similar to a circuit breaker, except that a circuit breaker opens a circuit and keeps it in the open position indefinitely, but a recloser may open and reclose the circuit several times in quick succession to allow a temporary fault to clear. A circuit breaker or recloser includes interrupters for physically separating the current-carrying contacts and an operating or switching mechanism for providing the energy necessary to accomplish separation of the contacts.
A linkage is provided for mechanically coupling the operating mechanism to each of the interrupters. In general, the linkages or mechanical couplings may be one of several types. For example, in a “push/pull” type coupling, conductive elements are moved into engagement when a rigid rod is moved in one direction, and the coupling elements are disengaged when the rod is moved in the opposite direction. In a rotational coupling, one of the conductive elements moves in response to the rotation of a bell crank as a link element between the three phases of the breaker rotates.
An example of such a mechanical coupling is illustrated in U.S. Pat. No. 5,569,891. FIG. 3 of this patent, which is reproduced herein as FIG. 1, shows a prior art example of a dependent pole mechanism for opening and closing all three phases of a circuit breaker simultaneously. In FIG. 1, a single connecting rod 22 connects operating mechanism 20 to two rotatable linking elements 25 and 26 by lever 24. The linking elements are coupled to bell cranks in the terminal portion of the interrupters (not shown). FIG. 4 of the patent, which is reproduced herein as FIG. 2, shows an example of a linkage for independent pole operation of the circuit breaker. In FIG. 2 herein, three independently operated connecting rods, 32, 33 and 34, are provided. Two of the connecting rods 32 and 33 are connected to lever assemblies 40 and 41 which couple the connecting rods to rotatable linking elements 37 and 39, respectively. Lever assemblies 40 and 41 also provide a mechanical bearing for decoupling connecting rods 32 and 33 from rotatable linking elements 38 and 36, respectively. The third connecting rod 34 is connected to a lever assembly that does not have a bearing for decoupling from a linking element. FIG. 6 of the patent, which is reproduced herein as FIG. 3, shows a lever assembly 40 having aperture 62 for mechanically coupling to one linking element and a hollow opening 63 with bearings 67 for decoupling from a second linking element. The lever assemblies are coupled to the one linking element by splining, pinning or bolting.
Rotating linkages that need to carry high energy loads without severe flexing or looseness have typically been made using multiple components with special splines and heavy bolted joints used to carry the loads. Typically these linkages allow for little axial alignment variation, have high stresses, and can become loose after many high load operations. These characteristics result in a high cost, dimensionally unforgiving, and failure prone design that requires careful manufacturing and detailed assembly procedures. There is a need for a linkage that overcomes the shortcomings of prior linkage designs.